toggle function for dom-attr

Description

A couple of the more used dojo capabilities I use are dom-class and dom-attr

In dom-class you kindly included a toggle function where we can either call toggle() or toggle(true|false).

However, dom-attr doesn't have an equivalent function and for doing things like toggling a disabled attribute, it would be useful to do:
domAttr.toggle(target,'disabled',null)
domAttr.toggle(target,'disabled',null,true)
domAttr.toggle(target,'disabled',null,false)

params:

target usual dom node options for target

attributeName

valueWhenTrue (if null, a valueless attribute would be added like <input disabled>...)

targetState (optional boolean)

Return would be resulting state (true/false)

I know the functionality may be accomplished through use of has, add, and remove on the existing class, it just seems like a toggle conspicuously absent.

The idea is to simplify code in a script where you know the attribute value you set on an element but may need to toggle it on/off so: